Water drainage pit for a fourdrinier machine



April 1955 K. o. ELDERKIN 2,706,434

WATER DRAINAGE PI T FOR A FOURDRINIER MACHINE Filed Jan. 11, 1951 4 Sheets-Sheet l lOl l l 1 01 O) O) INVENTOR 3 KARL o. ELDERKIN April 19, 1955 K. o. ELDERKIN WATER DRAINAGE PIT FOR A FOURDRINIER MACHINE 4 Sheets-Sheet 2 Filed Jan. 11. 1951.

INVENTOR KARL O. ELDERKIN ATTORNEY April 19, 1955 K. o. ELDERKIN WATER DRAINAGE FIT FOR A FOURDRINIER MACHINE Filed Jan. 11, 1951 '4 Sheets-Sheet a INVENTOR KARL O- ELDERKIN ATTORNEY April 19, 1955 K. o. ELDERKIN WATER DRAINAGE FIT FOR A FOURDRINIER MACHINE 4 Sheets-Sheet 4 Filed Jan. .11. 1951 ii ii wn Om INVENTOR ELDERKIN ATTORNEY United States Patent WATER DRAINAGE PIT FOR A FOURDRINIER MACHINE Karl 0. Elderkin, Crossctt, Ark., assignor to Crossett Lumber Company, Crossett, Ark., a corporation of Arkansas Application January 11, 1951, Serial No. 205,564

6 Claims. (Cl. 92-44) This invention relates to the manufacture of paper, and particularly to improvements in the water drainage and recirculation system at and adjacent the wire pit of a Fourdrinier machine, especially of the type operating at high wire speed using a pressure type head box.

In Fourdriniers of this type, many thousands of gallons of water per minute are drained from the stock through the wire into the wire pit, and from there recirculated, with added fiber, back to the head box and thence again to the wire, by means of a pump which draws the water from the pit and supplies the fiber-water stock under pressure to the head box. It is the primary object of this invention to achieve a more uniform flow of stock at constant velocity from the head box onto the Fourdrinier wire to the end that the sheet of paper formed on the wire at high speed is of uniformly constant thickness.

Irregularities in the paper formed on the Fourdrinier wire result principally from pressure pulsations at the head box caused by entrained air in the recirculated water passing through the pump. In accordance with my invention, turbulence in the water flow which causes air entrainment is greatly reduced and whatever air is entrained is given the opportunity to escape during a slow initial descent of the water in draining from the pit. A high static water pressure is imposed on the suction side of the pump to minimize the effect of whatever air may still be retained. Retention of entrained air by flocculated fiber is minimized by an effective mode of removal of such fiber.

In the drawings:

Fig. 1 is a plan view of the wire pit.

Fig. 2 is a vertical section of the wire and pit on the line 22 of Fig. 1.

Fig. 3 is a vertical section of the wire and pit on the line 3-3 of Fig. 1.

Fig. 4 is a diagrammatic elevation to show comparative weir levels.

Fig. 5 is a diagrammatic plan view indicating the surface plan of the water in the wire pit.

A Fourdrinier machine embodying the present invention includes the usual wire 2 (Fig. 2) supported by table rolls as it is led from the head box 4 over the saveall pans 6 and 8 and over suction boxes 11 from which it returns around end rolls 12 and bottom rolls 13 to the roll 14 at the head box. A number of showers 15 clean the wire as it returns to the head box, the water from the showers passing through the wire and draining into the wire pit in the conventional manner. The water, draining from the sheet that has been laid on the wire, falls into the saveall pans 6 and 8 and is returned to the wire pit 20 in a novel manner to be described. From the wire pit the water is drawn through an opening 22 at the bottom of the pit, through the suction conduit 24 leading to the fan pump 26 which forces the water back to the head box 4 through conduit 28. Fiber is added at the suction conduit 24, in the usual way.

The wire pit 20 is believed novel in its construction and mode of operation. It extends in the direction of wire travel from the vertical wall 30 below and behind the head box to the vertical wall 32 below the suction boxes. The pit extends transversely a distance approximating the wire width from vertical wall 34 (Fig. 3) to vertical wall 36. From the vertically sided top opening thus defined, the side and end walls of the pit slope downwardly to the opening 22, centrally of the bottom of the pit, as indicated by the front and rear walls 38, 40 and the side walls 50, 52. The water is maintained in the wire pit at 2,706,434 Patented Apr. 19, 1955 the approximate level indicated at A, by weirs as will be described, and the water is replenished by drainage from the saveall pans and showers and by added so-called makeup water, as will appear.

In the embodiment illustrated, two saveall pans are employed, saveall pan 6 receiving drainage water from perhaps one-fourth to one-third of the wire and saveall pan 8 draining from the remaining three-fourths or twothirds of the wire, the arrangement preferably being such that the two pans drain approximately equal quantities of water and the different lengths of the two pans representing the greater amount of drainage from the stock when initially laid down. Pan 6 drains into downspouts 60 and 62 on opposite sides of the machine and pan 8 similarly drains into downspouts 64, 66. To facilitate such drainage, the bottoms of the pans are appropriately sloped as indicated by the slope downwardly from the center line to the sides at 8a, 8b, for the pan 8 (Fig. 3) and the slope downwardly from front and rear (Fig. 2) at the portions designated 8c 8d. The pan 6 is similarly constructed.

The downspouts 62, 66 on the right side of the machine lead downwardly to a common downspout header 70 which extends nearly the full length of the top opening of the wire pit behind the vertical wall 36, as indicated in Fig. 2, terminating at the ends 70a, 70b (Fig. 2). A similar downspout header 72 extends along the left side of the pit to receive drainage through downspouts 60, 64. At intervals along each header are arranged inlets for communication into the wire pit, each inlet being partially covered by an adjustable gate by which the size of the inlet opening may be regulated. Typical inlets at both sides are indicated at 74, 76 (Fig. 3) with adjustable gates 78c and'80c respectively, defining openings 79 on both sides of the pit. The gates for the right side are shown at 78a through 78 (Fig. 2) and corresponding gates are arranged on the left side. Each inlet, as indicated by inlet 76 (Fig. 3) preferably has an upwardly inclined top wall 76a which joins the vertical side wall 34 of the pit approximately at the water surface, with the gate adjusted downwardly therefrom to provide the opening 79 of desired size, the opening being substantially entirely disposed below the water surface.

At the suction box end of the wire pit (Fig. 2) the vertical wall 32 is formed at its upper edge as a weir 90, referred to as the make-up water weir. Spaced from the make-up water weir by the trough 92 is a so-called white water overflow weir 94. Water received from the suction boxes and referred to as make-up water is introduced to the trough 92 and flows over the weir into the wire pit. Excess Water from either the wire pit or trough 92 drains over the overflow Weir 94 into the white water pit and is removed from the system. 96 designates the usual couch pit.

At the head box end of the pit, the vertical end wall 30 is formed at its upper end as a skimming weir 98, effective, by a limited overflow, to skim from the surface of the water in the wire pit flocculated fiber which floats on the surface of the water, the fiber being carried into the trough 100 and appropriately drained out of the system. Drainage over weir 98 is controlled by valve 101 (Fig. 1) at one end of trough 100, the other end 103 being closed.

The side walls 50, 52 of the wire pit are formed with ledges 102, 104 which catch heavy foreign bodies falling into the pit to keep them from falling through the bottom opening 22 and thence into the suction duct 24 and pump 26.

The comparative weir and water levels are indicated by the simplified diagram of Fig. 4. In general, the normal level of the water in the pit, designated A, depends upon the elevation of the overflow weir 94 which is at substantially the elevation of the tops of the inlet openings 79 so that these openings are just below the water surface. The skimming weir 98 is just below the level of the overflow weir 94 so that the foam and floating fiocculated fiber are skimmed off by flow over the skimming weir, as regulated by the valve 101 in trough 100. The make-up water weir 90 is considerably lower than the skimming and overflow weirs so that make-up water readily enters the pit. For height adjustment of the overflow and skimming weirs 94 and 98 aromas they are provided with adjustable weir plates 95 and 97, respectively (Fig. 2). The levels of the various inlet openings and weirs relative to each other and to the approximate normal water level, aid in establishing the flow pattern on the surface of the water in the pit as illustrated in Fig. 5.

In the particular embodiment of my invention illustrated, the inlet openings are about 1 /2" and the elevations of the weirs and inlets below the top edge of the wire pit are as follows:

(1) The normal water level 2'1" (2) The top of the downspout header inlet openings 2'1 (3) The skimming weir 2'2 (4) The make-up Water weir '6" (5) The overflow weir 21%" In operation, the wire pit is filled with water up to the level indicated at A. The wire is started moving at the desired speed which may be of the order of 2,000 feet per minute as an approximation. The fan pump 26 pumps water from the wire pit through the suction conduit 24 to the head box. The water is discharged from the head box onto the wire. The water falls through the wire to the saveall pans 6 and 8 and from the saveall pans travels through the downspouts 60, 62, 64 and 66 to the downspout headers 70, 72 from which is discharges back to the wire pit through the openings 79 afforded by the adjustable gates. After the above procedure has been established, paper-making fiber in the proper quantity is added at the suction conduit 24 so that thereafter a mixture of fiber and water is laid down on the wire from the head box and the machine is in operation for making paper.

The adjustable gates 78a to 78 and 80a to 80f, discharge the water laterally through openings 79 which are at and below the approximate level of the water surface. Thereby, the water is backed up through the downspout headers and the downspouts to the saveall pans so that free falling or cascading of the water which would entrap air is minimized.

As indicated by Fig. 5, the water entering the pit from the openings 79 is spread out over the surface of the pool of water in the pit so that bubbles of air that may be entrained readily rise to the surface without having to travel vertically any substantial distance through the water, and thus the air is readily removed. The pool is deep and devoid of substantial turbulence in its flow. Make-up water flowing over the weir 90 from trough 92 enters the pit, as shown in Fig. 5 at 105, and joins the flow 112, 114 from the side openings so that the foam and flocculated fiber are directed generally toward the center of the pool as indicated Where, under the influence of entering make-up water, they flow gradually in the direction of the skimming weir and are skimmed off.

Because the walls near the top of the pit are vertical, the pit water descends relatively slowly at first, gradually accelerating as the walls of the pit converge, thus allowing time for air entrapped in the water to bubble out. The adverse effect of any air that may remain entrapped and be carried with the water to the pump is minimized by the high hydrostatic pressure on the suction side of the pump as a result of the substantial pit depth, which may be of the order of about 25 feet or even more. In the pit shown, the vertical top sides extend downwardly about one-fifth of the pit depth for slow descent of the water, after which the acceleration is gradual to the discharge opening 22 by virtue of the sloping side or bottom walls.

Thus, the drainage and recirculation system provided by my invention greatly lessens air entrainment by assur ing that the water draining from the wire is conducted, with a minimum of cascading or turbulence, into the pit where the entering water is spread out over the surface of the pool where it remains while any air that may have been entrained is allowed to escape and the foam and flocculated fiber which would impede such escape is skimmed off, allowing the water then to discharge at a static head which lessens the effect on the pump of any air which may still be entrained. Thereby, I assure against appreciable pulsations in flow through the recirculation pump so that the spouting velocity of the .fiber and water from the head box is constant as required for uniformity in thickness of the paper formed on the wire.

I claim:

1. In a Fourdrinier machine a water drainage and recirculation system, comprising a pit having opposite side walls, weir means for maintaining the water at a predetermined level in the pit, ducts extending along both opposite side walls of the pit and having orifices adjacent the water level so that the water from the ducts enters the pit and flows laterally from both sides toward the pit center line, the said weir means including a skimming weir located at one end of the pit and a make-up water weir disposed at the opposite end of the pit from the skimming weir, and means for introducing make-up water over the make-up water weir to induce surface flow of the water in the direction of the skimming weir so that foam and floating flocculated fiber are skimmed off.

2. In a Fourdrinier machine a water drainage and recirculation system comprising a pit having opposite side walls, weir means for maintaining the water at a predetermined level in the pit, ducts extending along both opposite side walls of the pit and having orifices adjacent the water level so that the water from the ducts enters the pit and flows laterally from both sides toward the pit center line, the said weir means including an overflow weir at one end of the pit, a skimming weir located at the opposite end of the pit and at an elevation below that of the overflow weir, a make-up water weir disposed adjacent the overflow weir and means for introducing make-up water over the make-up water weir to induce surface flow of the water in the direction of the skimming weir so that foam and floating flocculated fiber are skimmed off.

3. In a Fourdrinier machine having a wire, a water drainage and recirculation system comprising a pit having opposite side walls, weir means for maintaining the water at a predetermined level in the pit, ducts extending along both opposite side walls of the pit and having orifices adjacent the water level so that the water from the ducts enters the pit and flows laterally from both sides toward the pit center line, pans beneath the wire to receive water draining therethrough, downspouts communicating with the pans and the orifices to conduct water from the pans to the orifices and adjustable gates at the orifices for adjustably restricting their size so that drainage water may be backed up in the downspouts to minimize water cascading in the downspouts.

4. In a Fourdrinier machine, having a wire, a water drainage and recirculation system, comprising a pit having opposite side walls, weir means for maintaining the water at a predetermined level in the pit, ducts extending along both opposite side walls of the pit and having orifices adjacent the water level so that the water from the ducts enters the pit and flows laterally from both sides toward the pit center line, pans beneath the wire to receive water draining therethrough, the bottoms of the pans being sloped to direct drainage water to the opposite side walls of the pit, downspouts located adjacent the side walls of the pit communicating with the pans and the orifices to conduct water from the pans to the orifices, and adjustable gates at the orifices for adjustably restricting their size so that drainage water may be backed up in the downspouts to minimize water cascading.

5. In a Fourdrinier machine the combination comprising a pit having side walls, ducts extending along the side walls, a wire and conduits for conducting water from the wire to the ducts, orifices in each of the ducts for admitting water from the ducts into the pit, an overflow weir at one end of the pit for determining the level of the water in the pit, the orifices being located at a level adjacent that of the overflow weir so that the water admitted from the ducts enters the pit adjacent the level of the water in the pit, a skimming weir located at the opposite end of the pit from the overflow weir at a level adjacent but below that of the overflow weir, and means for admitting make-up water adjacent the overflow weir and directing the make-up water along the surface toward the skimming weir, whereby the surface water, including foam and flocculated fiber, are caused to flow toward the center of the tank and thence toward one end thereof and over said skimming weir.

6. The machine as defined in claim 5 which also includes pans for collecting the water from the wire, downspouts for conducting the water from the pans downwardly to said ducts and adjustable gates over said orifices for narrowing their size so that the water backs up in the downspouts to avoid cascading and aeration.

References Cited in the file of this patent UNITED STATES PATENTS 718,406 Webb Jan. 13, 1903 6 Parker Aug. 14, 1906 Poirier Jan. 10, 1933 Campbell Jan. 12, 1937 Schyder Feb. 22, 1944 Witham Apr. 4, 1944 Hornbostel May 30, 1950 FOREIGN PATENTS Germany Oct. 25, 1939 

